Unable to get free space for drive: M
(21, 'GetDiskFreeSpaceEx', 'The device is not ready.')
Unable to get free space for drive: L
(21, 'GetDiskFreeSpaceEx', 'The device is not ready.')
Unable to get free space for drive: N
(21, 'GetDiskFreeSpaceEx', 'The device is not ready.')

So calibre will not connect to it. If your reader is actually working, then you can use the connect to folder function in calibre to connect to it instead.